2000-04-20 04:00:00 PDT Regional -- Today is April 20, and the significance of the date could be religious or infamous, depending on whom you ask.

But for many who describe themselves as members of the counterculture, April 20 -- or 4/20 -- is a day to celebrate the pleasures of altered consciousness, loosen the bonds of convention and, in short, slack off and smoke a lot of pot.

This afternoon, as the clock strikes 4:20 p.m., thousands of people across the United States will be gathered on college campuses, in city parks, private homes and on mountain tops to observe what some refer to as "the stoner's New Year," or "Miller Time for hippies."

In San Francisco, the Fourth Annual 420 Hemp Fest will kick off at 4 p.m. at Maritime Hall, and in Marin County, revelers plan to gather atop Mount Tamalpais for a ritual smoke-out. In Ann Arbor, students at the University of Michigan will have their annual Hash Bash, and in Washington, D.C., legalization activists will kick off a fund-raiser for their yearly Fourth of July smoke-in in front of the White House.

If you've never heard the term 420 (that's "four-twenty," not "four hundred and twenty") used in quite this way, you're not hip -- but you're not alone. The term has eluded the understanding of those in the straight-and-narrow world for nearly 30 years.

And if you do know what 420 refers to, odds are that you have no idea where the term came from. Ever since 420 became an insider's catchphrase in the 1970s, theories as to its origin have multiplied like Starbucks outlets, raising it to the level of urban myth.

"It has become a giant urban myth and it's a lot of fun," said attorney Keith Stroup, executive director of the National Organization to Reform Marijuana Laws, or NORML. "Folks who smoke have a lot of fun with this code word, and the rest of the country doesn't know what the hell we're talking about."

Devotees will insist that 420 is the penal code section for marijuana use, or the police radio code for marijuana smoking in progress, or the number of chemical compounds in marijuana, or that April 20 is the date that Jim Morrison died. Unless it was Jimi Hendrix, or was that Janis Joplin?

All these theories, and dozens more, are wrong, wrong, wrong.

For the record, 420 of the California penal code refers to obstructing entry on public land. The number is not a police radio code, and the number of chemical compounds in marijuana is 315, according to the folks at High Times magazine, who should know. Morrison died on July 3, Hendrix on September 18, and Joplin on October 4.

According to Steven Hager, editor of High Times, the term 420 originated at San Rafael High School, in 1971, among a group of about a dozen pot-smoking wiseacres who called themselves the Waldos. The term 420 was shorthand for the time of day the group would meet, at the campus statue of Louis Pasteur, to smoke pot.

"Waldo Steve," a member of the group who now owns a business in San Francisco, says the Waldos would salute each other in the school hallway and say "420 Louis!" The term was one of many invented by the group, but it was the one that caught on.

"It was just a joke, but it came to mean all kinds of things, like 'Do you have any?' or 'Do I look stoned?' " he said. "Parents and teachers wouldn't know what we were talking about."

The term took root, and flourished, and spread beyond San Rafael with the assistance of the Grateful Dead and their dedicated cohort of pot-smoking fans. The Waldos decided to assert their claim to the history of the term after decades of watching it spread, mutate and be appropriated by commercial interests.

The Waldos contacted Hager, and presented him with evidence of 420's history, primarily a collection of postmarked letters from the early '70s with lots of mention of 420. They also started a Web site, waldo420.com.

"We have proof, we were the first," Waldo Steve said. "I mean, it's not like we wrote a book or invented anything. We just came up with a phrase. But it's kind of an honor that this emanated from San Rafael."